The major efforts of our group at present molecular level into the life cycle of the human retroviruses, particularly human immunodeficiency virus type-1 and human T cell leukemia virus type-I. The following areas are addressed: (1) analyses of the viral regulatory genes, especially tat, tax, rev and -rex; their interactions with cellular factors which influence their activity; and their effects on expression of cellular genes. For example, we have partially elucidated the mechanism of induction of lymphotoxin expression by tax, in collaboration with investigators at the University of Vienna; (2) studies on the regulation of viral ribonucleic acid polymerase promoters in different cell types; (3) studies on the regulation of viral gene expression at the level of ribonucleic acid splicing. This work involves comparing transcript expression and processing in different cell types, in different diseases and their stages of progression, and under the influence of extrinsic factors such as cytokines; (4) comparison of the proviral integration status with viral gene expression; and (5) development of anti-viral treatments based on the above studies.